Field of the Invention
The invention relates to an arc quenching configuration for an electrical switching device. The electrical switching device has a dielectric material enclosure, which is assembled from a lower part and an upper part in a plane parallel to its width faces, as well as input and output connections between which a current path having at least one contact point is located. The contact point must be opened in the event of an over-current or a short-circuit current. Any arc which occurs in the contact point, which may have either a stationary contact piece and a moving contact piece or two fixed contact pieces (disposed at a distance from one another) and a contact link with moving contact pieces, is fed during a disconnection operation to an arc splitter stack, in which the arc is quenched.
Circuit breakers preferably have a contact point, with the moving contact piece being disposed on a contact lever; motor circuit breakers preferably have two stationary contact pieces, which are bridged by a contact link. Where there is one contact point, only one arc splitter stack is provided while, in contrast, where there is a double contact point, two such stacks are provided. The arc splitter stack has a number of arc splitter plates, which are held at a distance from one another by insulating paper; the individual arc splitter plates subdivide the arc into small individual arcs, thus resulting in an increased arc voltage, which is in the opposite direction to the power supply system voltage and ensures current limiting. The greater the number of plates, the higher the arc voltage can be. However, this is dependent on the arc remaining stable in the arc splitter plate chamber. When a number of plates are used, there is a high risk of the arc sections being short-circuited at the side, at the rear or else in front of the plates, thus resulting in a smaller arc voltage, with the arc voltage oscillating severely. Furthermore, there is a risk of the arc not burning in a stable manner in the arc splitter plate chamber, but in fact being able to have a tendency to run out of the deionization chamber, so that the mean arc voltage is reduced, and oscillates once again.
In order to improve the stable burning of the arc within the arc splitter stack, it has become known for at least one arcing plate to be coated with a suitable plastic layer. Thus, once the foot of the arc has run into the deionization chamber, it is stabilized in the chamber.
If the coating material is a gas-releasing material, the gas pressure within the arc splitter stack can be increased, thus also increasing the arc voltage since a gas atmosphere exists between the coated arc splitter plates, and this can be used to increase the arc voltage that exists there.
It is accordingly an object of the invention to provide an arc quenching configuration for an electrical switching device that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which improves even further the arc quenching configuration of the type mentioned initially.
With the foregoing and other objects in view there is provided, in accordance with the invention, an arc quenching configuration for an electrical switching device. The electrical switching device has a dielectric material enclosure with side faces and formed from a lower part and an upper part in a plane parallel to the side faces. The arc quenching configuration contains a stationary contact piece, a moving contact piece, and an arcing chamber for producing an arc between the stationary contact piece and the moving contact piece during a switching operation. The stationary contact piece and the moving contact piece are at least partially disposed in the arcing chamber. Guide rails are provided and lead from the arcing chamber. An arc splitter stack has a number of arc splitter plates and is disposed downstream of the guide rails. The arc passes between the guide rails into the arc splitter stack. The arc splitter plates have a given external circumference. At least one further plate composed of an insulating material is disposed in or adjacent to the arc splitter stack. The at least one further plate has an external circumference corresponding substantially to the given external circumference of the arc splitter plates. The at least one further plate further has an internal recess formed therein.
Accordingly, the at least one plate is composed of insulating material and is preferably located inside or outside the arc splitter stack and its external circumference can project beyond the external circumference of the arc splitter plates, and it has an internal recess.
According to one preferred refinement of the invention, the internal recess may have an inlet constriction area and a widened area, of which the inlet constriction area is open to the contact point.
The configuration results in that the conditions within the arc splitter stack can be monitored more efficiently and the individual parameters can be better matched to one another.
Furthermore, an optimized gas pressure can be produced within the arc splitter stack by the plate having a suitable thickness and by a suitable choice of materials, so that the arc voltage between the individual arcing plates is increased without, however, the arc being passed back to the contact point as a result of an excessively high gas pressure. This makes it possible to better monitor the stable burning of the arc within the arc splitter stack, the arc voltage is increased and, in consequence, the prospective short-circuit current is limited better and more safely.
The plastic PA 6 or else the plastic PA (6xe2x80x946) may be used, by way of example, as the material whose gas releasement is optimum for the purpose of arc quenching.
According to a further embodiment of the invention, the inlet constriction area may have straight boundary edges; however, it could also widen in a V-shape toward the contact point.
The widened area of the internal recess may have an approximately rectangular or, possibly, also an approximately circular internal contour.
It could also be state that the internal recess is keyhole-shaped.
In one particular embodiment of the invention, the at least one plate is fitted such that it bounds the arc splitter stack on one side.
A further refinement according to the invention provides for the at least one plate composed of insulating material to be integrally formed entirely or partially on the inner face of at least one part of the dielectric material enclosure of the electrical switching device. For the assembly process, this offers the advantage that a standard arc splitter stack can be used, which is inserted into the enclosure such that the plate, which is integrally formed on the inner face of the enclosure, bounds the arc splitter stack on a side. There is no need to modify the arc splitter stack itself, because the plate composed of the insulating material is integrally formed as a part of the enclosure, on its inner face, and is also composed of the same material as the enclosure.
One particularly advantageous refinement option for the fitting of the plate according to the invention provides that the plate is divided into two halves along a division axis which runs parallel to its longitudinal sides and between them, with in each case one of the two halves being integrally formed on the inner face of one of the two dielectric material enclosure parts. When the dielectric material enclosure containing the upper part and lower part is joined together, the two plate parts are then joined together along the division axis, seamlessly, to form the complete plate. The two plate parts are in this case joined together, in particular, such that the way in which their external contours are joined together forms the internal contour of the internal recess in the plate.
The particular advantage of the invention is that the switching capacity is improved and increased, and the disconnection response is stabilized; furthermore, the air gaps and creepage distances can be increased in an configuration with an arc quenching chamber between the contact pieces, with an elongation which is used as a guide rail.
The invention can be used in all switching devices in which an arc that occurs during a switching operation is quenched by a quenching device, or serves to stabilize the arc at a specific point.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an arc quenching configuration for an electrical switching device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.